This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Rev1 is a key part of the DNA replication machinery and is found in all eukaryotes. Translesion synthesis is the process by which errors that continually occur within the genome are identified and replicated through to enable the high fidelity polymerases to complete their function of replicating the genome. The Y family of DNA polymerases encompasses a variety of enzymes specific for different types of DNA lesions and different stages in the bypass process. In the case of Rev1 the enzyme is highly specific for incorporation of cytidine opposite a G that has an N2 adduct. A previous structure solved in our lab of the yeast enzyme indicated a unique method of specifying the incoming nucleotide via a protein template. It is hoped that this work will give insights into the mechanism seen in the human enzyme and identify novel domains associated with different functions to the yeast protein.